Process and apparatus for forging metals



June 9, 1959 J. HAVLIK PROCESS AND APPARATUS FOR FORGING METALS Filed July 10, 1957 5 Sheets-Sheet 1 O T N E V N JAQSLAV HAVLIK ATTo gEYs June 9, 1959 J. HAVLIK 2,890,324

PROCESS AND APPARATUS FOR FORGING METALS Filed July 10, 1957 v 5 Sheets-Sheet 2 mvzm'oa /5' JAP sLAv HAVLIK ATTOmE J. HAVLIK PROCESS AND APPARATUS FOR FORGING m'mgns Filed July 10, 1957 June 9, 1959 r 3 Sheets-Sheet 3 INVENTOK JAP sLAv HAVLIK ATTomP/s United States Patent PROCESS AND APPARATUS FOR FORGING METALS Jaroslav Havlik, Preston, Ontario, Canada Application July 10, 1957, Serial No. 670,924

Claims. (Cl. 219-149) This invention relates to a process and apparatus for forging metals.

More particularly, my invention is directed to heating metal by resistance while held in forging position in a closed die, and forging in one continuous operation or at a predetermined interval without removing the metal from the heating position.

I am fully aware of the common practice of heating metal by resistance either with or without electric current pulsation, for the purpose of upsetting or gathering stock into an open die or electrode. This is accomplished by heating the metal by means of resistance to produce a plastic portion but leaving a hardened section to propel the plastic metal into an open die.

In conventional forging processes, it is necessary to heat the material in a furnace remote from the forging die, resulting in loss of heat and plasticity during the time it is being removed from the furnace and positioned in the die for forging. This restricts the amount of flow practicable in a given heat, results in multiple heats" and operations, and is costly from the point of view of labour and time.

Furthermore, I have found that conventional furnace heating necessitates holding the material at high temperatures for long periods of time, to permit complete penetration of the heat throughout the metal, resulting in oxidation and heavy scaling on the finished forging. This can be minimized only with elaborate equipment by immersing the heating and forging processin an inert atmosphere.

Also, it is well known that standard forging practice results in a relatively high amount of scrap due to mis location of metal in the die.

I have observed that my process and apparatus are particularly useful for heating and forging titanium, due to the peculiarities encountered in heating titanium for forging.

Although titanium has an extremely high melting point (3020 F.), two major problems are encountered when it is heated for forging, as follows:

(a) When heated above 1200 F., and particularly in excess of 1650 F., and exposed to hydrogen and/or oxygen for extended periods, the absorption of these gases will be extensive enough to produce an embrittled alloy.

(b) When heating in excess of approximately 1800 F. (depending upon the alloy) for extended periods, a beta transformation takes place which destroys the physical values of the alloy.

In applying my resistance heating and forging process to titanium, it was found to be practical to forge at efficient temperatures (2000 F. to 2400 F.), and neither absorption nor transformation occurred to any appreciable degree due to the extremely short heating and forging period.

One of the objects of my invention is to heat and forge the material between electrodes which are integral with dies, to confine the steps of heating and forging within 'ice the area between the dies. By so doing, the metal is confined in the area between the dies and will be forced to flow into the precise contour of the dies by pressure exerted thereon.

Another object of this invention is to provide an assembly of forging members including forging dies and electrodes, which are capable of withstanding pressures limited only to the physical characteristics of the die material.

Another object of my invention is to produce completed forgings in one continuous operation to dimensional tolerances heretofore impracticable, which are free from scale and flash, with excellent grain flow and metallurgical properties, and with a minimum wastage of material.

An object of this invention is to produce forgings automatically and continuously and to eliminate time and temperature loss due to the previous need of conveying material from furnace to die. Also, it virtually disposes of the need for highly skilled forging operators.

A further object is to eliminate re-heating and thus avoid loss of metal values in metals such as titanium.

The proper distribution of heat is essential to place the correct amount of heat in the proper area of the metal to enable eflicient forging at optimum conditions. For example, by heating the bar so that the maximum heat is found at its center portion, with diminishing heat towards the ends, the center portion will flow first to fill the extremities of the die, and a completely finished product maybe made without multiple forging steps.

Throughout the process, the electrodes and die supports are water-cooled to avoid overheating of the electrodes, die supports and forging member.

The apparatus for my process includes a power-operated press, a die and supporting members, electrodes forming part of said die connected to a source of electric power, means for cooling said die, supporting members and electrodes, insulation for avoiding excess leakage of electric current from said electrodes to said die, and means for controlling the current to said electrodes.

In the accompanying drawings,

Figure 1 is a front elevation of an hydraulic press illustrating the arrangement of dies, electrodes, electric current supply and water cooling according to my invention;

Figure 2 is a front elevation partly in cross-section of the dies and electrodes, with a metal piece in position for heating and forging;

Figure 3 is a similar view showing the completed forgs;

Figure 4 is a detail view of the electrode showing the manner of fixing a hard cap on the contact surface of the electrode;

Figure 5 is a detail view showing the hard cap fixed to the contact surface of the electrode.

Like reference numerals refer to like parts throughout the specification and drawings.

Any suitable power-operated press may be used in carrying out my invention, such as the hydraulic press 10 illustrated in part in Figure 1. Full details of the press and its controls are not illustrated as they are common knowledge.

A steel punch 11 is mounted on the upper operating platform 14 of press 1!), and a die 12 is mounted on the lower operating platform 15, in any conventional manner, the punch 11 and die 12 having electrodes 1%, 17 formed therein connected to an electric power supply 18 by means of flexible shunt 19, and bus-bar 20.

The steel punch 11 is shown mounted on a punch base member 21, and the die 12 is mounted on a die base member 22 to impart support during the forging operation.

The construction of the steel punch 11, die 12 and electrodes 16, 17 will now be described in detail.

It will be apparent from the drawings that the elec trodes 16, 17 are formed integrally with the punch 11 and die 12, respectively. For better conductivity, the electrodes 16, 17 are made of a copper alloy which is relatively soft compared with the punch 11 and die 12. Therefore a cap 23, 24 made of a suitable hard alloy is secured to the respective operating ends the electrodes 16, 17 on punch 11 and die 12 in the following manner.

It was found to be impracticable to attach a hard facing to the copper electrodes 16, 17 by means of brazing or soldering as the joint fractured due to slippage of ma-- terial when forging pressures were applied.

Also, it was found to be impracticable to join the cop per electrodes 16, 17 to shunt 19 and bus-bar 20 by means of soldering or brazing and effectively sealing the water-- cooling circuit, due to slippage and subsequent growth of material during forging.

The above problems were overcome by forming the cap with a dovetail 25 and fitting it over a cut-away 26 on electrode 17 as shown in Figure 4. With a metal billet 27 in position on cap 24, forging pressure is applied permitting the copper in the cut-away 26 to upset into the recess formed by the dovetail. 25, and thus riveting the cap 24 to electrode 17.

O ring seals 28 are provided on the electrodes 16, 17 to seal electrode Water channels and permit lateral growth. and vertical movement during the application of forging pressure.

Electrodes 16, 17 are formed integrally with punch 11, and die 12, respectively and are insulated therefrom by insulation 29. Insulation 30 is provided between the base i of the electrode 16 and the punch base member 21, and between the base of the electrode 17 and the die base member 22. Insulation 29, 30 extends along the copper bus-bars 31, 32 to prevent leakage of current to punch 11, die 12 and base members 21, 22.

The electrodes 16, 17 are formed of a slug of copper alloy with a central hollow cavity 33, 34. A hollow tube 35, 36 is mounted in cavity 33, 34 by a metal slug 37, 38 and a hole 39 is drilled through the base of the electrode and the slug 37, 38 to provide a channel into the cavity 33, 34 through the tube 35, 36. is provided in the electrode 16, 17 adjacent to the slug 37, 38. Water is fed from a source of supply, such as a tap, through conduit 43, 44 attached to hole 39, 40, thence passes through tube '35, 36 into cavity 33, 34 and is discharged through exit channel 41, 42 through exhaust conduit 45, 46 to any suitable drain.

The punch 11 and die 12 may be in any desired form according to the forging which is to be produced. In the present embodiment the punch 11 and die 12 is for a flat circular disc 50 with a raised centre 51 and flanged rims 52, forged from the sheared bar 53, as shown in Figures 2 and 3. However, it will be apparent that any form of punch and die may be used which may be formed integrally With an electrode to provide a one-step heating and forging operation according to this invention. Therefore, I do not wish to be limited to the particular form of punch and die illustrated herein.

In the operation of this process, a cold sheared or cut bar 53 is placed on the cap 24 of electrode 17 in position to be contacted by cap 23 of electrode 16. Then the electrode 16 is brought into contact with the upper end of the bar 53 which engages with the cap 23 and an initial pressure is applied by press 10 to hold the bar 53 firmly and ensure a good electrical contact between electrodes 16, 17 through the bar 53. This step of the process is shown clearly in Figure 2.

Current is then applied in pulses from source 13, through bus-bars 31, 32 and through electrodes 16, 17 to An exit channel 41, 42

heat bar 53 by resistance to the temperature required to forge at maximum efficiency.

I have found that heating by resistance may be accomplished most efficiently by applying a series of regulated current pulsations to the bar and thus allow the heat to soak through the metal for uniform heating. However, it is understood that heating by resistance may be carried out by a steady application of current within the scope of my invention, according to known practices.

It is pointed out also that the number and duration of the heating and soaking periods of the above current pulses and the current and voltage values will depend upon the characteristics of the metal and the size of the bar to be forged. Therefore, it is not intended to limit the scope of the invention in this respect.

When the bar 53 has been heated to the desired forging temperature, forging pressure is applied through press 10 and the bar 53 is forged efiiciently without removing the bar from its position. This step of the process is shown clearly in Figure 3. Inasmuch as the ends of the metal bar are in contact with the water-cooled electrodes, they are relatively cool to the body of the bar and provide a slightly hardened portion to propel the metal into the die cavity.

Current can be applied during forging to compensate for any heat lost due to contact with the die.

The process is completely automatic from the first step of feeding the bar into the die 12 down to the production of the finished forging free from scale and flash with excellent grain flow and very close tolerance. Thus, it is apparent that the process is adaptable for use in large scale production of forgings continuously and automatically without the drawbacks of articles produced according to known upsetting, multiple forging, and resistance upsetting methods heretofore in use.

Throughout the heating and forging operations, the punch 11, die 12, electrodes 16, 17 and surrounding parts are cooled by circulation of water as described hereinabove. Of course, the type of metal being heated, current values and other factors must be taken into consideration in maintaining adequate heating to the maximum eflicient forging temperature.

It will be observed that due to the extremely short heating cycle and relatively instantaneous forging operation, the period during which the metal is maintained at an elevated temperature and exposed to oxidation is reduced to a minimum. Obviously, this is an important factor in reducing scaling and oxidation to a minimum.

Also, it is relatively simple to isolate the equipment from the atmosphere to eliminate oxidation and resulting scaling.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a process for heating and forging titanium in a two-piece die automatically and in one operation, comprising the steps of inserting a titanium bar to be forged into disc shape in a die, applying a controlled initial contact pressure to the die to hold said titanium bar in the die, rapidly heating the titanium bar, controlling the distribution of heat throughout the area of the titanium bar by regulated periods of heating interrupted by regulated soaking periods during which the heat diffuses through the titanium bar, maintaining the heated titanium bar in the die until the bar is heated to correct forging temperature, and then applying a controlled forging pressure to said die to forge the bar within the die, the total time interval for heating and forging being limited within a range to maintain the physical values of the titanium and to avoid substantial beta transformation and absorption.

2. In an apparatus for heating and forging metal, a two-piece die having an upper punch member and a lower die member mounted in a press and adapted to receive a metal bar to be forged therebetween, hollow electrodes integral with the upper punch member and lower die member insulated from the press, a hard pressure member of electrical and thermal conductivity on the contact surface of each electrode, cooling power supply means, means for controlling the heat in the hollow electrodes and the die, and means for applying heat and pressure to forge the metal piece within the die.

3. In an apparatus for heating and forging metal, a two-piece die having an upper punch member and a lower die member mounted in a press and adapted to receive a metal bar to be forged therebetween, hollow electrodes of high electrical and thermal conductivity integral with the upper punch member and lower die member insulated from the press, a relatively hard, substantially non-deformable pressure member of electrical and thermal conductivity on the contact surface of each electrode, power supply means, cooling means for controlling the heat in the hollow electrodes and the die, and means for applying heat and pressure to forge the metal piece within the die, the electrodes and the pressure members together forming a combination pressure member and conductor for the transmission of heat and pressure for forging the metal piece within the die.

4. In a heating and forging apparatus as set forth in claim 3, wherein the pressure member and the electrode are rigidly connected by means of a dovetail fitting.

5. In a heating and forging apparatus as set forth in claim 3, wherein the pressure member is provided with a flanged dovetail and the base of the electrode is provided with a recessed portion and said dovetail and recessed portion being riveted together by forging pressure.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR HEATING AND FORGING TITANIUM IN A TWO-PIECE DIE AUTOMATICALLY AND IN ONE OPERATION, COMPRISING THE STEPS OF INSERTING A TITANIUM BAR TO BE FORGED INTO DISC SHAPE IN A DIE, APPLYING A CONTROLLED INTITIAL CONTACT PRESSURE TO THE DIE TO HOLD SAID TITANIUM BAR IN THE DIE, RAPIDLY HEATING THE TITANIUM BAR, CONTROLLING THE DISTRIBUTION OF HEAT THROUGHOUT THE AREA OF THE TITANIUM BAR BY REGULATED PERIODS OF HEATING INTERRUPTED BY REGULATED SOAKING PERIODS DURING WHICH THE HEAT DIFFUSES THROUGH THE TITANIUM BAR, MAINTAINING THE HEATED TITANIUM BAR IN THE DIE UNTIL THE BAR IS HEATED TO CORRECT FORGING TEMPERATURE, AND THEN APPLYING A CONTROLLED FORGING PRESSURE TO SAID DIE TO FORGE THE BAR WITHIN THE DIE, THE TOTAL TIME INTERVAL FOR HEATING AND FORGING BEING LIMITED WITHIN A RANGE TO MAINTAIN THE PHYSICAL VALUES OF THE TITANIUM AND TO AVOID SUBSTANTIAL BETA TRANSFROMATION AND ABSORPTION. 